TRACER DIFFUSION ON CORRELATED HETEROGENEOUS SURFACES

Tracer diffusion on heterogeneous surfaces is studied by Monte Carlo s imulations. The energetic surface topography is described by a dual si te-bond model where site and saddle points (bond) energies are incorpo rated in a general way. The case of uniform energetic distributions is studied and the behavior of the diffusion coefficient is analyzed for several topographies: random traps, random barriers, random sites-bon ds, correlated traps, correlated barriers, and correlated sites-bonds, for different correlation degrees. The conditions under which the tem perature dependence of the tracer diffusion coefficient shows a non-Ar rhenian behavior are discussed. The jump correlation factor is also an alyzed since the jump mechanism plays a fundamental role in this treat ment. Surface diffusion emerges as an important tool for the character ization of the energetic topography on heterogeneous surfaces.